Thermodynamic Initial Guess Retrieval (TIGR)
Description of the TIGR dataset
The Thermodynamic Initial Guess Retrieval (TIGR) data set, in its latest version, is a climatological library of 2311 representative atmospheric situations selected by statistical methods from 80,000 radiosonde reports (Chédin et al., 1985; Achard, 1991; Chevallier et al., 1998). Each situation is described, from the surface to the top of the atmosphere, by the values of the temperature, water vapour and ozone concentrations on a given pressure grid.
Several datasets are associated with the above mentioned atmospheric profiles :
- The radiances (or equivalently the brightness temperatures) a satellite borne instrument (e.g. TOVS, ATOVS, AIRS, IASI, Modis, Seviri, IIR, etc..) would have observed under several conditions of observation (satellite zenith angle, surface characteristics, etc...).
- The transmittances and Jacobians (partial derivatives of the brightness temperature with respect to temperature, gas concentration for H2O, O3, CO2, N2O CO, CH4, etc., surface temperature and emissivity).
Radiances, transmittances and jacobians profiles are generated using the 4A forward radiative transfer model.
Since 1985, the TIGR dataset knew several versions :
- TIGR : 398 atmospheres (1985)
- TIGR1 : 1207 atmospheres
- TIGR2 : 1761 atmospheres
- TIGR3 : 2311 atmospheres
- new tropical atmospheres (profiles 1 to 872)
- mid-lat and polar atmospheres unchanged (profiles 873 to 2311)
- TIGR2000 : 2311 atmospheres
- TIGR3 +
- The ozone profile is deduced from the Ugamp climatology (Li and Shine, 1995)
- change in the longitude convention : -180:+180
- TIGR2000_6CORPS : 2311 atmospheres
- ATMOS measurements have been used to improve the extrapolation of the water vapour towards the upper pressure levels.
Characteristics of the new version are given below.
Available version of TIGR
A new version (dated May 2010) and referenced as 'atm4atigr2000_v1.2_43lev' is now distributed whose main characteristics are given below.
Air mass classification of TIGR
As in the preceding version, the TIGR dataset includes 2311 atmospheres. These atmospheric situations are stratified by a hierarchical ascending classification into five airmass types (Tropical, temperate -Midlat1-, cold temperate and summer polar -Midlat2-, Northern Hemisphere very cold polar -polar1-, winter Polar -Polar2-), depending of their virtual temperature profiles (Achard, 1991; Chédin et al., 1994).
|Tropical||1 to 872|
|Mid-lat1||873 to 1260|
|Mid-lat2||1261 to 1614|
|Polar1||1615 to 1718|
|Polar2||1719 to 2311|
Specificities of the current version
- Pressure range : to take into account the capability of high spectral resolution instruments or limb viewing instruments to sound high levels of the atmosphere, the pressure range has been extended up to 0.0026 hPa (instead of 0.05hPa in the preceding version). Accordingly, the number of levels is equal to 43 (instead of 40 in the preceding versions).
- Temperature profiles : between 37 hPa and 0.05 hPa (levels 18 and 4 respectively), temperature profiles have been replaced by a monthly climatology (*) from the ERA_Interim reanalyses and then extrapolated up to 0.0026 hPa (level 1) based on the Ace_Scisat Instrument level 2 outputs.
- Water vapour profiles : between 380 hPa and 0.05 hPa (levels 32 and 4 respectively), water vapour profiles have been replaced by a monthly climatology (*) from the ERA-Interim reanalyses, and then extrapolated up to 0.0026 hPa (level 1) based on the Ace_Scisat Instrument level 2 outputs.
- Ozone profiles : originally based on an UGAMP climatology, the ozone profiles have been replaced between the surface and 0.05 hPa (levels 43 and 4, respectively) by a monthly climatology (*) from the ERA-Interim reanalyses, and then extrapolated up to 0.0026 hPa based on the Ace_Scisat Instrument level 2 outputs.
Every initial profile of TIGR is collocated in time and space with the corresponding ERA-Interim climatology according to the following rules :
- The space collocation is based on a simple nearest neighbour method.
- The year is randomly chosen among the twelve corresponding years of the climatology.
Included in this TIGR package are the following elements
- atm4aTIGR2000_v1.2_43lev.dsf :The TIGR database (atmospheric description).
- readme.TIGR2000_v1.2_43_lev.doc : The related readme.
- lecTIGR2000.f : A fortran 77 source program to read the TIGR database.
- atm4aTIGR2000_v1.2_43lev.ref : As reference, output of the lecTIGR2000.f fortran program when run at LMD. This output is in ascii format, rearranged by columns (Pressure, Temperature, Water vapor, Ozone) and by lines, each line describing a pressure level.
The TIGR Database is available as a freeware product but only for academic use and to those wishing to use the code for scientific research.
For a purpose other than a research or academic use please, contact-us.
To obtain a copy of the latest release of the database, please complete the Licence Agreement by way of the TIGR database Online registration form. The Licence Agreement must be printed, signed and either faxed to +126.96.36.199.52.18 or sent to :
Laboratoire de Météorologie Dynamique
Analyse du Rayonnement Atmosphérique
Route départementale 36
91128 PALAISEAU CEDEX
On receipt of the signed Licence Agreement, the TIGR Database will be made available.